With the rapid changes in the mode of living and the general social orientation towards greater convenience, the so-called fast or convenience foods account for a major proportion of food consumed today. These foods are generally manufactured by processes involving a heating step such as baking and, after such heat-treatment, they are frequently filled with various fillings such as vegetable salads, meat sauces, meat patty, jam, chow mein, spaghetti, egg, fish meat, chocolate, peanut butter and what not.
However, the incorporation of such fillings is more often than not carried out manually, so that the procedure is not as hygienic as required, nor is it sufficiently quantitative. Thus, the process does not lend itself to mass production. Furthermore, when fluid or juicy fillings such as curry roux, mapo doufu, etc. are to be incorporated, it is difficult to preclude penetration or leakage of their moisture into the host food material and even if the consistency is pre-adjusted with starch or the like, it is inevitable that, the use of such a tackifier deteriorates the palatability and flavor of foods. Similarly, fillings which melt on exposure to heat, such as chocolate, ganache, jellies, peanut butter and so on, too, can hardly be incorporated in the host or substrate food prior to heating because of their inherent nature.
Meanwhile, the production of a proteinaceous container is a known technology as disclosed in U.S. Pat. No. 3,310,446 but this product is a water-soluble container manufactured using a large quantity of a wetting agent and is intended for packaging dry ingredients which are to be dissolved or dispersed in water. Moreover, the materials contained are not "fillings" in the correct sense of the term. Further, yuba or dried bean curd, which is a traditional Japanese food, is logically a kind of proteinaceous casing material but it has never been used in the form of a pouch or the like.
Further, it is inconvenient to heat-seal a protein film and then fill the resultant casing with fillings manually. Moreover, when the fillings are high in water content and of low viscosity, the filling operation is not easy even by a manual procedure. And even today when we are seeing remarkable progresses in packaging technology and witnessing many cases of implementation, we do not know of a case in which the incorporation of fillings, particularly moist ingredients, in edible film casings has ever been performed continuously and mechanically.